Porous membranes are widely used as separation media in a variety of applications, including, for example, filtration and fuel cell gas diffusion paper. When porous membranes are used in aqueous environments, surface hydrophilicity on the membranes is often desirable to facilitate water transport through the membranes.
One method for incorporating hydrophilicity into porous membranes includes in-situ polymerization of hydrophilic monomers onto the substrate surface. A potential problem related to such coating deposition methods (e.g., depositing hydrophilic acrylate coatings) is that the membrane often suffers from gradual hydrophilicity loss as a result of coating loss during its use. Another potential problem with such a method is that hydrophilic monomers intrinsically do not wet hydrophobic membranes. This may lead to an uneven distribution of the hydrophilic coating over the entire surface of the hydrophobic membrane after curing takes place.
Another method for incorporating hydrophilicity into porous membranes includes surface grafting hydrophilic monomers onto a substrate. In principle, the surface grafting method may offer a solution to the coating stability problem described above, in part because of the robust chemical bonding between hydrophilic functional groups and the substrate used in the grafting method. However, the grafting method generally involves sophisticated chemistry that is highly dependant on the substrate material selected.
As such, it would be desirable to provide a simplified method for introducing substantially stable surface hydrophilicity onto porous membranes.